Two major aspects of carbohydrate metabolism will be investigated. In the first of these, the role of defective gluconeogenesis in Sudden Infant Death Syndrome will be examined by assaying specific gluconeogenic enzymes in liver and kidney tissue from victims of this disease. Blood samples from infants at random and from siblings of SIDS victims will be drawn immediately before the first morning feeding and analyzed for blood sugar and for malic acid as a means of determining the efficacy of gluconeogenesis and the functional activity of the enzyme phosphoenolpyruvate carboxykinase. The second aspect of carbohydrate metabolism to be studied deals with the role of "futile metabolic cycles" in non-shivering thermogenesis and in malignant hyperpyrexia. Using a method we have already published, we will measure rates of the fructose 6-yields (reversibly) fructose diphosphate and of the glucose yields (reversibly) glucose 6-P futile cycles in tissues of experimental animals requiring different amounts of thermal energy to maintain their body temperature. Thyroid hormones are known to play a role in thermogenesis and their influence on these futile cycles will be measured. We will examine in detail the mechanism that triggers futile cycling in the malignant hyperpyrexia induced by halothane in a strain of susceptible pigs.